This invention relates in general to improvements in die casting machines and, in particular, to an apparatus for improving shot rods used in die casting machines.
More specifically, but without restriction to the particular embodiment and/or use which is shown and described for purposes of illustration, this invention relates to a die casting shot rod which eliminates excessive wear between the shot rod and shot sleeve, increases die casting efficiency, minimizes plugging of oil holes used for lubricating the shot rod, and improves distribution of lubricants by dispersing a precise and controlled amount of lubricant directly to the parting line between the shot rod tip and the shot cylinder or shot sleeve.
In die casting operations, the injection system is fundamental to the production of high quality castings, for example, by controlling the pressure and volume of the metal during and after die cavity fill, as well as the velocity with which the metal is injected. In performing this operation, the shot system is critical to the operation of the die casting machine and the quality of the castings it produces.
As known to those skilled in the art, the shot system functions to introduce metal into the die cavity in a manner dependent upon the particular metal alloy being used. However, regardless of what particular metal alloy is being employed in the die casting machine, contact between the alloy and the structural components of the injection system, must be minimized in order to avoid excessive wear or deterioration of the machine or system components. For example, when casting aluminum alloys a cold chamber process is used. The injection system for such a cold chamber process comprises, generally, a cylinder mounted onto a fixed platen. At one end the cylinder protrudes through the platen into a running system of the die cavity, while at the other end a plunger is activated by the injection system. A hole or entrance port is formed in the upper side of the shot cylinder and has molten aluminum poured therethrough.
Each time the plunger is advanced through the shot sleeve, metal is injected into the die cavity. Thereafter, the die is opened and a casting is removed with the plunger returning to its initial position to complete the cycle. While the injection system utilized with the cold chamber process can be complex and differ in design due to the materials being used, in principle the method of working is the same. Hydraulic pressure is applied to a piston, which moves the plunger forward to make the casting and retracts back to its original position.
In operation, such a shot system is prone to many different problems. Excessive wear and poor lubrication frequently occur between the enlarged plunger tip and the shot sleeve, as well as dripping and wasting of the lubricant used to minimize the wear. Lubrication of these contiguous surfaces has heretofore suffered from inefficiency and plugging of the lubricating lines and the lubricating holes causing excessive wear and parts fatigue. The cleaning of these lubricating holes or ports has been difficult and time consuming, while excess lubrication and improper lubrication creates a smoke emission problem during die casting operation. All of these problems add up to excessive maintenance.